Principal Investigator / Author(s): Adams, William C.

Contractor: University of California, Davis

Contract Number: A4-070-33

The primary purposes of this research were to: (1) investigate whether healthy young adult females are more sensitive to high ambient concentration of nitrogen dioxide (NO2), ozone (03), and NO2 plus 03 than their male counterparts;(2) determine the duration of enhanced responsiveness upon re-exposure to O3 at intervals of 1 to 5 days and (3) study the physiologic mechanisms associated with pulmonary function and airway resistance effects observed upon 03 exposure. Ninety-four healthy young adults, including 20 females, undertook 60 minutes of heavy bicycle ergometer exercise, which elicited an average minute ventilation volume of approximately 8 times greater than that at rest. Subjects were exposed via an obligatory mouthpiece inhalation system to filtered air and to 03 concentrations of either 0.30 or O-35 parts per million (ppm). In one study, subjects were also exposed to 0.60 ppm NO2 and to 0.60 ppm NO2 plus O.30 ppm 03. Measurement of standard pulmonary function tests, including airway resistance, pre- and post exposure, together with periodic observations of exercise ventilation, respiratory metabolism, and subjective symptoms of respiratory discomfort, were obtained. In one study, respiratory system impedance was measured to assess the relative effect of 03 on central and peripheral airways. It was observed that Inhalation of 0.60 ppm NO2 for 1 hour, while engaged in heavy, sustained exercise, does not elicit significant physiological effects evidenced by measurement techniques used in this study, nor evoke additive effects in combination with 0.30 ppm 03 in healthy young adults- The possibility remains, however, that peripheral airway effects of NO2 in combination with 03 at these concentrations, as recently revealed in histological evidence in exercising rats by others, may have occurred. Young adult females were found to evidence similar responses to 03 and to O3 Plus NO2 inhalation as young adult males when their 1 hour exercise pulmonary ventilation rate was proportional to the gender difference in lung size. In accord with previous work of others, we observed an enhanced responsiveness upon re-exposure to 0.35 ppm 03 within 24 hours. While this greater response may persist for 48 hours in some apparently more sensitive individuals, it is absent upon 72 hours or more after initial exposure.

For questions regarding this research project, including available data and progress status, contact:
Heather Choi
at (916) 322-3893